Arguments about the Constitution’s interpretation and about what judges or other political actors do often refer to legitimacy. What does legitimacy mean and what does it have to do with constitutions?

Political legitimacy is a property of regimes or systems of government. Legitimacy is not the same thing as justice, although (a certain degree of) justice is one component of legitimacy. Although many systems of government are unjust in one way or another, they can also be minimally legitimate; moreover, their legitimacy may increase if they become more just.

Legitimacy combines three different aspects: sociological, procedural, and moral. Sociological legitimacy concerns the degree to which the public accepts the government's authority to govern, settle disputes, enforce its laws and maintain order. Sociological legitimacy also concerns the degree of trust and confidence that people have in a regime. Thus sociological legitimacy depends on whether the governing regime appears fair and just to the public (as opposed to whether it actually is fair and just), and whether it is appears to be efficacious, that is, whether it can deliver government services and maintain security and social order. Procedural legitimacy concerns the degree to which state officials gain power and use it through regular procedures and authorized legal processes. Moral legitimacy concerns the degree to which the government's decisions and actions are just, moral and praiseworthy.

Judgments of legitimacy usually are a combination of these factors. Consider, for example, the concept of democratic legitimacy, which is a type of political legitimacy concerned with the degree to which the government is ruled by or responsive to "the people," however these terms are defined. Democratic legitimacy, like other forms of political legitimacy, depends on a combination of sociological, procedural and moral legitimacy. A state is democratically legitimate to the extent (1) that people view the government as their government and as responsive to them (sociological legitimacy); (2) that people are able to choose their leaders, replace them, and hold them accountable through free and fair methods (procedural legitimacy); and (3) that the government respects political values of public participation, free expression, and equal citizenship (moral legitimacy).

Democratic legitimacy may be consistent with a fair degree of injustice and human suffering in a regime, because democratically legitimate orders may adopt very unwise and unjust policies and may fail to protect important rights. Nevertheless, democratic legitimacy usually requires at least some fair procedures and some rights of political participation; and sociological legitimacy may demand that people recognize that the legal system protects their basic rights and the rights of others. These features contribute to the political system’s moral legitimacy without guaranteeing justice.

A state is illegitimate if it lacks a minimum level of legitimacy (that minimum, and whether particular regimes satisfy it or have satisfied it, is hotly contested). Above that threshold, however, legitimacy is a matter of degree; states can have greater or lesser degrees of legitimacy. A system of government is minimally legitimate if it has a sufficient combination of sociological, procedural and moral legitimacy. The precise combination is also a matter of great dispute. Put differently, a system of government is minimally legitimate is sufficiently stable, efficacious, just, and can maintain the acceptance of the vast majority of the people who live under it. It must be stable enough to allow ordinary politics to occur and allow law abiding people to live their lives and plan for their futures. It must be efficacious enough to maintain order, deliver government services, maintain a legal system that includes courts and law enforcement, settle disputes, and defend the public from foreign invasion and domestic disorder. It must be sufficiently just to be worthy of respect by reasonable persons within the system, by giving them sufficient reason to submit themselves to its authority and enjoy the benefits of political union. And the vast majority of people who live within the system must accept it as having the authority to govern them.

In previous work, I’ve argued that a successful constitution like America's must simultaneously serve three functions: It must be basic law-- a framework for governance that allocates powers and responsibilities. It must be higher law-- a source of aspiration and a reflection of values that stand above ordinary law and hold it to account. And it must be our law-- an object of attachment that we see as the product of our collective efforts as a people. Viewing the Constitution as our law involves a collective identification with those who came before us and those who will come after us. The Constitution as our law constitutes us as a people that extends over time. This collective identification is a constitutional story that allows us to regard the Constitution as our own even if we never officially consented to it.

What is the relationship between these functions of a constitution and the political legitimacy of the regime that is structured by the constitution?

Constitutional systems contribute to but do not guarantee the legitimacy of governments that live within them. First, as noted above, constitutional systems can produce very unjust results and very unwise policies. Second, events like wars, economic depressions, famines, health crises and other calamaties can undermine the government's ability to deliver services, maintain order and defend the public frome external threats. Sometimes, of course we can blame the poor design of the constitutional system for bringing these problems on, exacerbating them or making it difficult to respond to them. But when governments fail or lose legitimacy it is not always because of defects in their constitutional system. Bad decisionmaking, poor judgment, economic collapse, plague, famine, insurrection or outside attack can undermine the legitimacy of otherwise just and well designed constitutional systems.

A constitution helps maintain and achieve legitimacy by succeeding at the functions mentioned: by serving as basic law, higher law, and "our law." These three constitutional functions promote the three different types of legitimacy-- sociological, procedural and moral-- in various ways. The basic law function of a constitution helps government be stable and efficacious, thus promoting public trust, confidence and support; it outlines basic procedures that produce a stable politics, and prescribes how power should be exercised and limited and how officials replace each other in an orderly scheme. The higher law function of a constitution gives people confidence that the long term project of their government is worthwhile; it gives people a language and an opportunity to criticize the system of government in practice, hold it to account and urge it to improve itself over time. Finally, a constitution that succeeds as "our law" keeps the constitution responsive to popular needs and values, helps people to identify with a collective project of governance that unites past, present, and future generations, gives people a stake in that project's continuation and its success, and generates fidelity and attachment to the constitution.

A constitutional system that succeeds as basic law, higher law, and as our law probably has a fair degree of democratic legitimacy, but it may be quite deficient in moral legitimacy. It may not protect some people’s rights in fact, even though it is committed to improvement over time and even if most citizens think the system is basically fair, just and honest. The history of the United States is a good example. Throughout much of the country’s history, the government engaged in practices that we would now regard as very unjust, and lacking in moral legitimacy, but the Constitution has by and large succeeded in its basic functions. It broke down at the time of the Civil War; what is more amazing is that it has not broken down regularly since then. My friend Sandy Levinson, of course believes that it is currently broken, and his primary indictment is that he believes it lacks democratic legitimacy.

I suppose that we are talking about institutional level legitimacy here.

An institution is presupposed not to be a black box. It has to interact with the environment; so there are two things going on, inputs into the "box" and outputs from it.

What action does a constitution perform? Well it is an actor in the sense it exerts decisive influence on governmental structures and laws. That can be seen as an output.

What is the input? Well, when we amend it.

A kind of functional legitimacy for institutions and constitutions is how well they "do" both: accept appropriate inputs and produce socially approved product.

An argument could be made that since practically speaking the Constitution is extremely hard to amend (i.e. it rejects inputs) than that is a de-legitimizing factor, even if it gets "A's" on the moral, procedural and sociological scales (which it currently doesn't).

"A system of government is minimally legitimate if it has a sufficient combination of sociological, procedural and moral legitimacy. ... Put differently, a system of government is minimally legitimate is sufficiently stable, efficacious, just, and can maintain the acceptance of the vast majority of the people who live under it."

A couple of comments:

1. If I understand you correctly you only address one kind of legitimacy (internal), but constitutions have to answer to another kind of legitimacy as well, the legitimacy of the process and procedure of producing the constitution (external). This can occur in circumstances of first impression, so to speak, such as the US Constitution, or in cases of rewriting, such as happened with the French constitution a few times. The moral or normative environment in which the constitution arises is important not only because it provides a source of legitimacy for the formation of the constitution, but it is the sea of norms by which the constitution and its manifestations can be judged. That is, in order to criticize a constitutional order one must have appeal to another set of legitimate norms. Those are sometimes referred to as international law, customary law, ius gentium or natural law. (I am not suggesting those are synonymous terms.). These non-constitutional sources of norms are those by which justice and morality are understood. Aristotle said a constitution exists prior to the writing, suggesting that something like what we understand as the sociological, if not the scientific, (in addition to the political) could play a role. That is, you say justice is a source of minimal legitimacy, but what is the source of these norms of justice?

2. The categories of “sociology,” “morality” and “procedure” are not of the same kind. Procedure is an aspect of morality, or justice. I am thinking of the concept of “due process.” If procedure is in the moral, that leaves us with the categories of sociology and morality. The moral invokes a deeply historical discourse in political science. In the broader academic context law is a sub-discipline of political science (and is clearly a subject of sociology). So, perhaps it would make more sense to say the relevant two categories are the social and the political. There must be social and political legitimacy. There are internal and external elements to each of those categories. For instance, a comprehensive discussion about migration could only be made if all four sources or areas of legitimacy were developed.

"An argument could be made that since practically speaking the Constitution is extremely hard to amend "

But IS the Constitution extremely hard to amend in a meaningful sense? Or is the lack of recent amendments a result of Congress not wanting amendments the states would gladly ratify, and not needing amendment it wants, because a supine judiciary 'interprets' the Constitution to give Congress any power it really wants?

If I want to do something somebody else is entitled to refuse to consent to, can I really say with any justice that the process for doing it is "extremely difficult" just because they refuse that consent? And by that reason cobble together a process which circumvents their ability to say no?

The assumption here seems to be that the federal government is somehow entitled to easily change the Constitution in any manner it sees fit, whether or not the states like it.